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Modbus Slave
Example
The M5Stack device, as a Modbus RTU slave, provides three continuously increasing 16 bit register values (D1/D2/D3) to the master station through function code 03 (read hold register), and can trigger data updates through button A.
from m5stack import *
from m5ui import *
from uiflow import *
from modbus.slave.rtu import ModbusSlave
import time
setScreenColor(0x222222)
inc = None
D1 = None
D2 = None
D3 = None
data_buf = None
title0 = M5Title(title="Slave Read Holding Register", x=62, fgcolor=0xFFFFFF, bgcolor=0xff3d00)
label0 = M5TextBox(16, 112, "From Slave to Master Send Register Data ", lcd.FONT_Default, 0xFFFFFF, rotate=0)
label1 = M5TextBox(41, 209, "Press A", lcd.FONT_Default, 0xFFFFFF, rotate=0)
label2 = M5TextBox(24, 55, "Text", lcd.FONT_DejaVu18, 0xFFFFFF, rotate=0)
label3 = M5TextBox(139, 55, "Text", lcd.FONT_DejaVu18, 0xFFFFFF, rotate=0)
label4 = M5TextBox(257, 55, "Text", lcd.FONT_DejaVu18, 0xFFFFFF, rotate=0)
def buttonA_wasPressed():
global inc, D1, D2, D3, data_buf
inc = inc + 1
if inc >= 2:
inc = 0
modbus_s.update_process(3, 10, 3, [D1, D2, D3])
pass
btnA.wasPressed(buttonA_wasPressed)
modbus_s = ModbusSlave(2, tx=17, rx=16, baudrate=9600, data_bits=8, stop_bits=1, parity=None, slaveID=4)
modbus_s.function_init(3, 10, 3)
D1 = 0
D2 = 0
D3 = 0
inc = 0
while True:
data_buf = modbus_s.receive_req_create_pdu()
if (modbus_s.find_function) == (3):
modbus_s.create_slave_response(data_buf)
wait_ms(10)
if inc:
D1 = D1 + 187
D2 = D2 + 231
D3 = D3 + 159
if D1 >= 0XFFFF:
D1 = 0
if D2 >= 0XFFFF:
D2 = 0
if D3 >= 0XFFFF:
D3 = 0
label2.setText(str(D1))
label3.setText(str(D2))
label4.setText(str(D3))
wait_ms(2)
API
print((str('code:') + str((1))))- Obtain function code
print(modbus_s.find_address)- Get device address
print((str('code:') + str((modbus_s.find_function))))- Obtain function code
print(modbus_s.find_quantity)- Obtain data volume
modbus_s = ModbusSlave(1, tx=17, rx=16, baudrate=9600, data_bits=7, stop_bits=1, parity=None, slaveID=1)- Initialize UART parameters
- Baud rate
- Data bits
- Checksum
- Equipment address
modbus_s.function_init(1, 0, 0)- Initialize coil status
print((str('ADU:') + str((modbus_s.receive_req_create_pdu()))))- Receive ADU request frames
modbus_s.create_slave_response()- Send ADU response buffer
modbus_s.update_process(1, 0, 0, [0, 0, 0])- Update functional parameters